Automobiles and other vehicles normally incorporate suspension systems designed to absorb road shock and other vibrations. Many vehicles are provided with independent suspensions located at each wheel. These suspensions are designed to independently minimize the effect of shock loading on each of the wheels.
Suspension systems commonly employ stabilizer bars which interconnect independent suspensions on opposite wheels and are effective to increase the roll rigidity and improve the steering stability of the vehicle. The stabilizer bars are connected to each wheel suspension by suspension links through ball joint assemblies.
Conventional ball joint assemblies comprise a ball stud seated in a socket. In a suspension link, each end of the link incorporates a socket, and a ball is seated in each socket. The stud, which extends from the ball in one ball joint assembly, is connected to a wheel suspension component. The stud extending from the ball in the other ball joint assembly is connected to one end of a stabilizer bar.
The socket in a ball joint assembly typically incorporates a bearing made from a plastic resin. The outer surface of the ball seats on the inner surface of the bearing and the stud extends out of the socket. The ball stud is free to move universally through a conical angle of approximately 30 degrees relative to the socket.
In prior art ball joint assemblies it was conventional to machine the ball surface to reduce friction between the ball and the bearing. It is also known in the prior art, as shown in Jackson U.S. Pat. No. 4,290,181, to construct a ball joint wherein a plastic bearing member is molded in the ball joint socket with the ball in place. Jackson states that the ball must be rotated while the bearing material congeals in order to form a suitable bearing surface.
The stud portion of the ball is conventionally connected to a wheel suspension component, for example, by fastening the component between a plate fitted onto an inner portion of the stud and a nut threaded onto the threaded outer end of the stud, as seen in Kidokoro U.S. Pat. No. 5,011,321. It is also known to form the plate integrally with the stud, in the form of a flange or collar, as seen in Shirai et al. U.S. Pat. No. 5,009,538.